Substituted pyrazolylpyrazole derivative and use of same as herbicide

ABSTRACT

Provided is a compound capable of effectively control worst weeds of higher leaf stages that present practical problems. A specific pyrazolylpyrazole derivative of formula (I) is disclosed that is able to solve the above-mentioned problems.

TECHNICAL FIELD

The present invention relates to a substituted pyrazolylpyrazole derivative and the use of that compound as an herbicide.

BACKGROUND ART

Numerous herbicides have recently come to be used in the cultivation of agricultural crops, and have contributed to reduced labor for farmers and improved productivity of agricultural crops. Numerous herbicides are also used practically in the cultivation of field and paddy rice.

However, there is considerable diversity in the species of weeds, the germination and growth periods of each species of weed are not uniform, and the growth of perennial weeds extends over a long period of time. Consequently, it is extremely difficult to control all weeds with a single spraying of herbicide.

Early to mid-term one-shot herbicides have been shown to be effective for paddy rice by treating during the second to third leaf stage of paddy weeds (generic term for Echinochloa oryzicola, Echinochloa crus-galli var.crus-galli, Echinochloa crus-galli var. formosensis, Echinochloa crus-galli var. praticola and Echinochloa crus-galli var. caudata), and major weeds can be controlled by a single treatment (see Non-Patent Document 1). However, it is extremely difficult to control paddy weeds that have grown to the 3.5 leaf stage or more with early to mid-term one-shot herbicides currently in practical use, and the control of paddy weeds in the third leaf stage and control of paddy weeds in the 3.5 leaf stage are technically completely different.

Moreover, maintaining herbicidal effects (residual activities) over a long period of time is important in terms of reducing spraying of agricultural chemicals, saving on labor and curtailing costs, and is considered to be an essential area of performance for early to mid-term one-shot herbicides.

In addition, acetolactate synthase (ALS) inhibitors have come to be widely used in recent years, and weeds exhibiting resistance to ALS inhibitors have become a problem. There are few herbicides demonstrating adequate efficacy against ALS inhibitor-resistant biotypes of the perennials of Sagittaria trifolia and Sagittaria pygmeae. In addition, examples of perennial weeds that have caused problems in recent years include Eleocharis kuroguwai, Scirpus planiculmis and Scirpus nipponicus, while examples of annuals include Aeschynomene indica, Leptochloa chinensis and Murdannia keisak, and there are few herbicides that demonstrate adequate efficacy against these difficult-to-control weeds.

On the other hand, numerous pyrazole derivatives are used practically as herbicides, and although pyrazole derivatives such as 4-(2,4-dichlorobenzoyl)-1,3-dimethyl-5-pyrazolyl p-toluenesulfonate (common name: “Pyrazolate”), 2-[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yloxy]acetophenone (common name: “Pyrazoxyfen”) or 2-[4-(2,4-dichloro-m-toluoyl)-1,3-dimethylpyrazol-5-yloxy]-4′-methylacetophenone (common name: Benzofenap”) are widely used, their registered application range for paddy weeds in Japan when used alone is up to the 1.5 leaf stage, and although these pyrazole derivatives are effective against a wide range of weeds, the efficacy thereof is not always adequate against paddy weeds of higher leaf stages.

In addition, although Compound 73 of Example 4 described in Patent Document 1 in the form of 1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-5-[methyl(prop-2-ynyl)amino]pyrazole-4-carbonitrile (common name: “Pyraclonil”) is effective against a wide range of weeds, its efficacy against paddy weeds of higher leaf stages is inadequate, and the registered application range in Japan against paddy weeds when using this herbicide alone is up to the 1.5 leaf stage.

CITATION LIST Patent Literature Document

-   Patent Document 1: WO 94/08999

Non-Patent Literature Document

-   Non-Patent Document 1: “Suiden Zasso no Seitai to Sono     Bojo—Suitosaku no Zasso to Josozai Kaisetsu (Ecology of Paddy Weeds     and their Control—Explanation of Weeds of Rice Paddy Crops and     Herbicide)”, p. 159

SUMMARY OF THE INVENTION Technical Problem

An object of the present invention is to provide a herbicide composition that has a wide herbicidal spectrum, is able to control worst weeds of higher leaf stages that present practical problems, and not cause phytotoxicity to crops such as paddy rice.

Solution Problem

As a result of conducting extensive studies to achieve the aforementioned object, the inventors of the present invention found that a pyrazolylpyrazole derivative having a specific chemical structure exhibits a wide herbicidal spectrum over a long period of time, demonstrates superior herbicidal efficacy against worst weeds of higher leaf stages, and has adequate safety with respect to cultivated crops, thereby leading to completion of the present invention on the basis of these findings. Thus, the present invention provides a pyrazolylpyrazole derivative in the form of a compound represented by the following formula (I):

wherein,

R¹ represents a halogen atom,

R² represents a cyano group or nitro group,

R³ represents a hydrogen atom, halogen atom, C₁-C₆ alkyl group (which may be substituted with one or more halogen atoms depending on the case) or C₁-C₆ alkoxy(C₁-C₆)alkyl group,

a represents 3 to 5, and

b represents 1 to 3.

In the present description,

a description in the manner of the previous “C_(a)-C_(b)” of each substituent refers to the number of carbon atoms respectively present in that group being from a to b.

Fluorine atoms, chlorine atoms, bromine atoms and iodine atoms are included in “halogen atoms”.

An “alkyl group” can be linear or branched, and although there are no limitations thereon, examples thereof include methyl, ethyl, n- or iso-propyl, n-, iso-, sec- or tert-butyl, n-pentyl and n-hexyl groups, and each is selected within a range of the specified number of carbon atoms thereof.

An “alkoxy group” refers to an alkyl-O-group in which the alkyl moiety has the above-mentioned meaning, and although there are no limitations thereon, examples thereof include methoxy, ethoxy, n- or isopropoxy, n-, iso-, sec- or tert-butoxy groups, and each is selected within a range of the specified number of carbon atoms thereof.

In the case of the “alkyl group”, at least one hydrogen atom contained in the substituent may be substituted with a halogen atom, and although there are no limitations thereon, examples thereof include chloromethyl, dichlororaethyl, trifluoromethyl, chloroethyl, dichloroethyl, trifluoroethyl, tetrafluoropropyl, bromoethyl, bromopropyl, chlorobutyl, chlorohexyl and perfluorohexyl groups, and each of these is selected within a range of the specified number of carbon atoms thereof.

In the case where the aforementioned group or moiety is substituted with a plurality of halogen atoms, that group can be substituted with more than one halogen atoms and/or substituents that are the same or different.

In all of the formulas listed below, substituents and symbols have the same meanings as defined for formula (I) unless specifically defined otherwise. The compound of formula (I) provided by the present invention can be easily synthesized by an alkylation reaction of a compound represented by formula (II).

The compound of formula (II) can be synthesized from tetrahydro-2H-pyran-2-ylideneacetonitrile or 5-chlorovaleryl chloride in accordance with the methods described in WO 93/10100 and WO 94/08999.

The compound represented by formula (II) can be synthesized by an alkylation reaction per se with reference to known reaction conditions (see, for example, WO 94/08999). This may also be carried out by a procedure consisting of protection of the amino group followed by alkylation and deprotection depending on the case.

The compound of formula (I) provided by the present invention has superior herbicidal efficacy and is useful as a herbicide as is clear from the results of the herbicidal activity tests described in Test Examples 1 to 3 to be subsequently described.

The compound of formula (I) of the present invention has activity against numerous types of crop weeds and non-crop weeds. Examples of cultivated plants include gramineous plants such as rice, wheat, barley, corn, oats or sorghum, broadleaf crops such as soybeans, cotton, beets, sunflowers or rapeseed, fruit trees, vegetables such as fruit vegetables, root vegetables or leafy vegetables, and grasses, and the compound of formula (I) can be used for the cultivation thereof.

The compound of the present invention has herbicidal efficacy against the various weeds listed below that cause problems in rice paddies in any of the treatment methods of soil treatment in an irrigated or unirrigated state, soil incorporation treatment and foliar treatment. Although the following lists examples thereof, these weeds are not limited to the following examples.

Examples of paddy weeds that can be controlled by the compound of formula (I) of the present invention include Alismataceous weeds such as Alisma canaliculatum, Sagittaria trifolia or Sagittaria pygmaea, Cyperaceous weeds such as Cyperus difformis, Cyperus serotinus, Scirpus juncoides, Eleocharis kuroguwai, Scirpus planiculmis or Scirpus nipponicus, Scrophulariaceous weeds such as Lindernia procumbens, Lindernia dubia subsp. dubia or Lindernia dubia, Pontederiaceous weeds such as Monochoria vaginalis or Monochoria korsakowii, Potamogetonaceous weeds such as Potamogeton distinctus, Lythraceous weeds such as Rotala indica or Ammannia multiflora, Asteraceous weeds such as Bidens tripartita or Bidens frondosa, Leguminoseous weeds such as Aeschynomene indica, Commelinaceous weeds such as Murdannia keisak, and Gramineous weeds such as Echinochloa oryzicola, Echinochloa crus-galli var. crus-galli, Echinochloa crus-galli var. formosensis, Echinochloa crus-galli var. praticola, Echinochloa crus-galli var. caudata, Leptochloa chinensis, Leersia japonica, Paspalum distichum or Leersia oryzoides.

In addition, the compound of the present invention has herbicidal efficacy against the various weeds listed below that cause problems in field land and non-crop land in any of the treatment methods of soil treatment, soil incorporation treatment and foliar treatment. Although the following lists examples thereof, these weeds are not limited to the following examples.

Examples thereof include broadleaf weeds, including Solanaceous weeds such as Solanum nigrum or Datura stramonium, Malvaceous weeds such as Abutilon avicennae or Sida spinosa, Convolvulaceous weeds such as Ipomoea pupurea, Amaranthaceous weeds such as Amaranthus lividus, Asteraceous weeds such as Xanthium strumarium, Ambrosia artemisiilifolia, Galinsoga ciliata, Cirsium arvense, Senecio vulgaris or Stenactis annuus, Brassicaceous weeds such as Rorippa indica, Sinapis arvensis or Capsella bursa-pastoris, Polygonaceous weeds such as Persicaria longiseta or Fallopia convolvulus, Portulacaceous weeds such as Portulaca oleracea, Chenopodiaceous weeds such as Chenopodium album, Chenopodium ficifolium or Kochia scoparia, Caryophyllaceous weeds such as Stellaria media, Scrophulariaceous weeds such as Veronica persica, Commelinaceous weeds such as Commelina communis, Lamiaceous weeds such as Lamium amplexicaule or Lamium purpureum, Euphorbiaceous weeds such as Euphorbia supina or Euphorbia maculate, Rubiaceous weeds such as Galium spurium, Galium spurium var. Echinospermon or Rubia argyi, Violaceous weeds such as Viola mandshurica, and Leguminoseous weeds such as Sesbania exaltata or Cassia obfusitolia, and Gramineous weeds such as Sorghum bicolor, Panicum dichotomiflorum, Sorghum halepense, Echinochloa crus-galli var. crus-galli, Digitaria ciliaris, Avena fatua, Eleusine indica, Setaria viridis, Alopecurus aequalis or Poa annua, and Cyperaceous weeds such as Cyperus rotundus.

Moreover, the compound of the present invention is also able to control a wide range of weeds growing in mowed swaths, fallow land, orchards, grasslands, lawn grass plots, train line caps, vacant land and forest land, or on farm roads, causeways and other non-crop land.

Moreover, the compound of formula (I) of the present invention does not demonstrate phytotoxicity that becomes a problem for paddy rice in the case of any cultivation method such as direct seeding cultivation or transplantation cultivation of paddy rice.

The compound of formula (I) of the present invention can be applied before or after plant germination and can be mixed into soil before seeding.

Although the dosage of the compound of formula (I) of the present invention can be varied over a wide range corresponding to the type of compound, type of target plant, application window, location of application, properties of desired effects and the like, and as a general reference thereof, the dosage can be within the range of about 0.01 g to 100 g, and preferably about 0.1 g to 10 g, as the amount of active compound per are.

Although the compound of formula (I) of the present invention can be used alone, a formulation assistant and the like is normally incorporated in the compound of formula (I) in accordance with ordinary methods, and although there are no limitations thereon, it is preferably formulated and used in any arbitrary drug form such as a dustable powder, emulsifiable concentrate, oil miscible liquid, solubilizing agent, suspo-emulsion, fine granule, aerosol spray, less drifting dust, micro granule fine, fine grains F, granules, wettable powder, water dispersible granules, flowable concentrate, throw-in types (Jumbo), tablets, paste, emulsion in oil, water soluble powder, water soluble granule, soluble concentration or capsule suspention.

There are no limitations on formulation assistants able to be used for formulation, and examples include solid vehicles, liquid vehicles, binders, thickeners, surfactants, anti-freezing agents and preservatives.

Examples of solid vehicles include, but are not limited to, talc, bentonite, montmorillonite, clay, kaolin, calcium carbonate, sodium carbonate, sodium bicarbonate, mirabilite, zeolite, starch, acidic clay, diatomaceous earth, chaoite, vermiculite, slaked lime, vegetable powder, alumina, activated carbon, sugars, hollow glass, silica sand, ammonium sulfate and urea.

Examples of liquid vehicles include, but are not limited to, hydrocarbons (such as kerosene or mineral oil), aromatic hydrocarbons (such as toluene, xylene, dimethyl naphthalene or phenyl xylyl ethane), chlorinated hydrocarbons (such as chloroform or carbon tetrachloride), ethers (such as dioxane or tetrahydrofuran), ketones (such as acetone, cyclohexanone or isophorone), esters (such as ethyl acetate, ethylene glycol acetate or dibutyl maleate), alcohols (such as methanol, n-hexanol or ethylene glycol), polar solvents (such as N,N-dimethylformamide, dimethylsulfoxide or N-methylpyrrolidone) and water.

Examples of binders and thickeners include, but are not limited to, dextrin, sodium salts of carboxymethyl cellulose, polycarboxylic acid-based polymer compounds, polyvinylpyrrolidone, polyvinyl alcohol, sodium lignin sulfonate, calcium lignin sulfonate, sodium polyacrylate, gum arabic, sodium alginate, mannitol, sorbitol, bentonite-based mineral matter, polyacrylic acid and derivatives thereof, chaoite and natural sugar derivatives (such as xanthan gum or guar gum).

Examples of surfactants include, but are not limited to, anionic surfactants such as fatty acid salts, benzoates, alkylsulfosuccinates, dialkylsulfosuccinates, polycarboxylates, alkyl sulfate ester salts, alkyl sulfates, alkyl aryl sulfates, alkyl diglycol ether sulfates, alcohol sulfate ester salts, alkyl sulfonates, alkyl aryl sulfonates, aryl sulfonates, lignin sulfonates, alkyl diphenyl ether disulfonates, polystyrene sulfonates, alkyl phosphate ester salts, alkyl aryl phosphates, styryl aryl phosphates, polyoxyethylene alkyl ether sulfate ester salts, polyoxyethylene alkyl aryl ether sulfates, polyoxyethylene alkyl aryl ether sulfate ester salts, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl aryl phosphate ester salts or salts of naphthalene sulfonate-formalin condensates, and nonionic surfactants such as sorbitan fatty acid esters, glycerin fatty acid esters, fatty acid polyglycerides, fatty acid alcohol polyglycol ethers, acetylene glycol, acetylene alcohol, oxyalkylene block polymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene styryl aryl ethers, polyoxyethylene glycol alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene hydrogenated castor oil or polyoxypropylene fatty acid esters.

Examples of anti-freezing agents include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol and glycerin.

Examples of preservatives include, but are not limited to, benzoic acid, sodium benzoate, methyl paraoxybenzoate, butyl paraoxybenzoate, isopropyl methyl phenol, benzalkonium chloride, chlorhexidine hydrochloride, aqueous hydrogen peroxide, chlorhexidine gluconate, salicylic acid, sodium salicylate, zinc pyrithione, sorbic acid, potassium sorbate, dehydroacetic acid, sodium dehydroacetate, phenoxyethanol, isothiazoline derivatives such as 5-chloro-2-methyl-4-isothiazolin-3-one or 2-methyl-4-isothiazolin-3-one, 2-bromo-2-nitropropane-1,3-diol and salicylic acid derivatives.

The previously mentioned solid vehicles, liquid vehicles, binders, thickeners, surfactants, anti-freezing agents and preservatives can each be used alone or in a suitable combination thereof corresponding to the purpose of use and the like.

Although the incorporated ratio of the compound of formula (I) of the present invention with respect to the total herbicide composition of the present invention can be increased or decreased as necessary and there are no particular limitations thereon, it is normally about 0.01% by weight to 90% by weight, and for example, in the case of being in the form of a dustable powder or granules, is preferably about 0.1% by weight to 50% by weight and more preferably about 0.5% by weight to 10% by weight, while in the case of being in the form of an emulsifiable concentrate, wettable powder or water dispersible granules, is preferably about 0.1% by weight to 90% by weight and more preferably about 0.5% by weight to 50% by weight.

These preparations can be provided for use in various types of applications by diluting to a suitable concentration as necessary followed by spraying or applying directly to plant foliage, soil or the surface of a rice paddy and the like,

The following provides an explanation of the present invention through examples thereof.

EXAMPLES Example 1 Method for the Synthesis of 1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-5-(but-3-ynylamino)pyrazole-4-carbonitrile (Compound 1)

Formic acid (18.4 g) was slowly dropped into acetic anhydride (33.7 g) cooled to 5° C. followed by stirring for 2 hours at 60° C. (Reaction Mixture A). Separate from the above, 5-amino-1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)pyrazole-4-carbonitrile (26.3 g) was dissolved in acetonitrile (200 ml) and stirred. The previously prepared Reaction Mixute A was slowly dropped therein and reacted for 1 day at room temperature and then for 4 hours at 60° C. The solvent was concentrated under reduced pressure followed by neutralizing using aqueous potassium carbonate solution, washing the precipitated solid with water and drying to obtain N-(1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-4-cyanopyrazol-5-yl)formamide (28 g).

N-(1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-4-cyanopyrazol-5-yl)formamide (50 g) was dissolved in acetonitrile (300 ml) followed by adding potassium carbonate (29 g) and stirring. 4-bromo-1-butyne (27.4 g) was added thereto followed by refluxing for 3 days. Following completion of the reaction, water was added followed by extraction with ethyl acetate. After drying with sodium sulfate, the solvent was concentrated under reduced pressure and the resulting crude product was purified by silica gel column chromatography (hexane/ethyl acetate=1:1) to obtain N-(but-3-ynyl)-N-(1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-4-cyanopyrazol-5-yl)formamide (20 g).

N-(but-3-ynyl)-N-(1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pryidin-2-yl)-4-cyanopyrazol-5-yl)formamide (20 g) was dissolved in ethanol (150 ml) followed by the addition of 10% hydrochloric acid (8.8 g) and refluxing for 1 day. Following completion of the reaction, water was added to the reaction liquid and the precipitated solid was filtered out to obtain the desired compound (15 g).

The starting material in the form of the compound of formula (II) was synthesized in accordance with WO 93/10100 and WO 94/08999.

The examples listed in the following tables can be synthesized by the same manner as the above-mentioned methods or obtained in the same manner as the above-mentioned methods.

TABLE 1 (I)

Compound R¹ R² R³ a b mp Refractive index (° C.) 1 Cl CN H 4 1 130-131 2 Cl CN H 3 1 3 Cl CN H 5 1 4 Cl CN Me 4 1 5 Br CN H 4 1 6 Br CN H 3 1 7 Cl NO₂ H 4 1 8 Br NO₂ H 4 1 <Preparation Examples>

1. Dustable powder Compound of formula (I) 10 parts by weight Talc 90 parts by weight A dustable powder is obtained by mixing the above components and finely crushing with a hammer mill. 2. Wettable Powder Compound of formula (I) 10 parts by weight Polyoxyethylene alkyl aryl ether sulfate 22.5 parts by weight   White carbon 67.5 parts by weight   A wettable powder is obtained by mixing the above components and finely crushing the mixture with a hammer mill. 3. Plowable concentrate Compound of formula (I) 10 parts by weight Polyoxyethylene alkyl ether phosphate 10 parts by weight Bentonite  5 parts by weight Ethylene glycol  5 parts by weight Water 70 parts by weight A flowable concentrate is obtained by mixing the above components and crushing using a wet pulverizer. 4. Emulsifiable concentrate Compound of formula (I) 15 parts by weight Ethoxylated nonylphenol 10 parts by weight Cyclohexanone 75 parts by weight An emusifiable concentrate is obtained by mixing the above components. 5. Granules Compound of formula (I)  5 parts by weight Calcium lignin sulfonate  3 parts by weight Polycarboxylate  3 parts by weight Calcium carbonate 89 parts by weight The above components are mixed followed by adding water, kneading, extruding and granulating. Subsequently, granules are obtained by drying followed by sizing. <Biological Testing Examples>

1. Paddy Herbicidal Activity Test

Rice paddy soil was filled into a 1/10000 are pot followed by the addition of suitable amounts of water and chemical fertilizer, kneading, seeding with Echinochloa crus-galli, Monochoria vaginalis and Scirpus juncoides and maintaining in an irrigated state at a water depth of 3 cm.

Wettable powder of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with a suitable amount of water, rice plants in the 2.0 leaf stage were transplanted during 3.5 leaf stage of Echinochloa crus-galli, and treated by dropping in chemical in the prescribed amount per are using a pipette.

After treating for 30 days in a glass greenhouse at an average atmospheric temperature of 30° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out by comparing growth inhibition rate (%) with an untreated group, while evaluation of phytotoxicity was carried out by comparing growth inhibition rate (%) with the state of a complete eradication group, and were evaluated at 11 levels indicated below.

0 (exponent): 0% to less than 10% (growth inhibition rate)

1: 10% to less than 20%

2: 20% to less than 30%

3: 30% to less than 40%

4: 40% to less than 50%

5: 50% to less than 60%

6: 60% to less than 70%

7: 70% to less than 80%

8: 80% to less than 90%

9: 90% to less than 100%

10: 100%

The results are shown in Table 2.

TABLE 2 5 g^(a.i.)/10 a 1 g^(a.i.)/10 a Echinochloa Scirpus Monochoria Rice Echinochloa Scirpus Monochoria Rice Compound crus-galli juncoides vaginalis plants crus-galli juncoides vaginalis plants 1 10 10 10 1 9 8 9 0 4.73 4 1 4 1 2 0 3 0  4.85, 4.156 3 1 3 2 2 0 1 2 4.131, 4.132 4 3 1 1 3 1 0 1

2. Farming Soil Treatment Test

Field soil was filled into a 1/6000 are pot followed by seeding with Digitaria ciliaris, Chenopodium album and Amaranthus retroflexus and covering with soil.

Wettable powder of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with water to the prescribed amount of chemical and uniformly sprayed onto each soil surface layer using 10 liters of sprayed water per are prior to weed growth following seeding.

After treating for 30 days in a glass greenhouse at an average atmospheric temperature of 30° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out in the same manner as the above-mentioned Test Example 1.

The results are shown in Table 3.

TABLE 3 10 g^(a.i.)/10 a 5 g^(a.i.)/10 a Digitaria Chenopodium Amaranthus Digitaria Chenopodium Amaranthus Compound ciliaris album retroflexus ciliaris album retroflexus 1 10 10 10 10 10 10 4.73 1 2 2 0 1 1  4.85, 4.156 4 5 6 3 4 3 4.131, 4.132 4 4 5 3 3 4

3. Weed Foliar Treatment Test

Soil was filled into a 1/6000 are pot followed by seeding with Digitaria ciliaris, Chenopodium album and Amaranthus retroflexus, covering with soil, and cultivating in a glass greenhouse at an average atmospheric temperature of 25° C.

Wettable powder of Target Compound (I) shown in Table 1 prepared in compliance with the preparation examples were diluted with water to the prescribed amount of chemical and uniformly sprayed onto the weeds using 15 liters of sprayed water per are when Digitaria ciliaris had grown to the 1.0 to 2.0 leaf stage.

After treating for 3 weeks in a glass greenhouse at an average atmospheric temperature of 25° C., the herbicidal efficacy thereof was investigated.

Evaluation of herbicidal efficacy was carried out in the same manner as the above-mentioned Test Example 1.

The results are shown in Table 4.

TABLE 4 10 g^(a.i.)/10 a 5 g^(a.i.)/10 a Digitaria Chenopodium Amaranthus Digitaria Chenopodium Amaranthus Compound ciliaris album retroflexus ciliaris album retroflexus 1 10 10 10 10 10 10 4.73 2 3 3 1 2 3  4.85, 4.156 5 6 6 3 5 4 4.131, 4.132 4 5 6 3 4 4

INDUSTRIAL APPLICABILITY

According to the present invention, the compound for formula (I) of the present invention is useful as a herbicide against harmful plants since it has superior herbicidal efficacy against undesirable plants. 

The invention claimed is:
 1. A compound represented by the following formula (I):

wherein, R¹represents a halogen atom, R²represents a cyano group or nitro group, R³represents a hydrogen atom, halogen atom, C₁-C₆ alkyl group which may be substituted with one or more halogen atoms, or C₁-C₆ alkoxy-C₁-C₆-alkyl group, a represents 3 to 5, and b represents 1 to
 3. 2. An herbicide composition comprising an herbicidally effective amount of at least one compound according to claim
 1. 3. The herbicide composition according to claim 2, further comprising a formulation assistant.
 4. A method for control of undesirable plants, comprising applying an effective amount of at least one compound according to claim 1 to an undesirable plant or a location of the undesirable plants.
 5. The method according to claim 4, wherein the at least one compound is applied to the undesirable plants among useful agricultural crops.
 6. A method for control of undesirable plants, comprising applying an effective amount of the herbicide composition according to claim 2 to an undesirable plant or a location of the undesirable plants.
 7. The method according to claim 6, wherein the herbicide composition is applied to the undesirable plants among useful agricultural crops.
 8. A method for control of undesirable plants, comprising applying an effective amount of the herbicide composition according to claim 3 to an undesirable plant or a location of the undesirable plants.
 9. The method according to claim 8, wherein the herbicide composition is applied to the undesirable plants among useful agricultural crops. 